Fix red develop 035a8dd4cb08

The merge lane found `develop` red at `035a8dd4cb0881ef9ad047c7273aab9b05dd2fac` on its own: no queued PR merges until it is fixed. Failing (tests and gate stages): - `docs-site-build-link-check` The whole gate log: artifact `12453` on lane task 11453. Make `develop` pass its full gate again. Open a PR as usual: the merge lane merges a PR that fixes some of these and adds no failure even while `develop` is red.

Fixed red develop (docs-site-build-link-check): two full gates on one tree raced the docs build because check.sh took its per-worktree full-tier lock after the stages had launched; the lock now comes first. Quick gate + suites green; PR #7398 queued in the lane.